Comparison FiiO M21 vs FiiO M17

Model of the digital-to-analogue converter installed in the device.

The DAC is one of the key components of any player: it converts the digital data recorded in the audio file into an analogue audio signal, which is fed through an amplifier to the headphones. The quality of the DAC directly affects how accurately the output sound will match the original signal, as well as whether the player can work with advanced digital signal formats: many of them require high computing power, which is not available in every DAC.

Note that the DAC model is indicated only if it is a high-end converter with above-average sound quality. On the modern market, in particular, DACs from such manufacturers are represented: AKM, Cirrus Logic, ESS Saber, Texas Instruments, Wolfson. And players with such equipment usually refer to Hi-Fi devices(see "Type").

It is also worth mentioning that the number of DACs can be different. The simplest option is one module for both sound channels, however, there are players equipped with two converters at once — one per channel. This "division of labor" affects the cost, but reduces the load on each individual DAC, which has a positive effect on the quality and reliability of the sound.

The range of audio frequencies that the player is capable of reproducing. The wider this range — the more complete the picture of the sound, the less likely that the device will "cut off" part of the sound spectrum. At the same time, when choosing this parameter, several points should be taken into account.

First, the average human ear is capable of hearing sounds from approximately 16 Hz to 20 kHz; deviations from these figures are small, and with age the range narrows even more. In fact, this means that for normal hearing, it is enough just to cover this gap. And the wider boundaries indicated in the characteristics of the player will be more of a marketing ploy than a really significant moment. Secondly, do not forget that the sound quality is determined not only by the range, but also by a number of other characteristics of the player — signal-to-noise ratio, frequency response, etc.; therefore, a wide range by itself does not guarantee a pleasing sound. And thirdly, the features of the audible sound also largely depend on the headphones used and their frequency range: all the advantages of a player with a wide frequency range can come to naught if the frequencies are “cut off” by the headphones.

The ratio between the level of the useful signal (clear sound) and extraneous noise, given by the player at the output. This parameter directly characterizes the quality of the built-in amplifier: it mainly takes into account the intrinsic noise of electronic circuits, and the higher the signal-to-noise ratio, the less these noises and the clearer the sound.

Note that in the case of players, this characteristic is often not particularly critical: the noise of the amplifier can be lost against the background of ambient sounds, especially in an urban environment, and for such situations even the most modest indicators, at the level of 70 – 80 dB, are enough. At the same time, for Hi-Fi models (see "Type") this moment is one of the most important; in the most advanced devices, the signal-to-noise ratio can exceed 120 dB.

The higher the power, the louder the sound you can get on the headphones, all other things being equal. In addition, higher power allows you to connect "ears" with higher impedance to the device (although there is no hard correlation here, and models with the same output power may have different headphone impedance limits). However, in the case of ordinary (non-Hi-Fi) players, this parameter is more of a reference than practically significant: usually, the power of the amplifier in such models is quite enough to “rock” most consumer-grade headphones. But for Hi-Fi devices (see "Type") models, output power is of key importance: it determines compatibility with high-resistance studio-class "ears". Detailed help on this issue can be found in special sources.

The nominal impedance (impedance) of the headphones that the player can handle normally.

Most consumer-grade headphones are 16 or 32 ohm impedance, which is supported by almost all modern players. Therefore, you should pay attention to this parameter only if you plan to use a device with high-quality "ears" of a studio or audiophile class. A characteristic feature of these headphones is high resistance, already in the hundreds of ohms, and not every player is suitable for them.

Also, it will not hurt to clarify the permissible headphone impedance if you are buying a Hi-Fi class device (see "Type"). Some of these models have a fairly high minimum resistance and are not compatible with standard 16 ohm (and sometimes 32 ohm) "ears".

The coefficient of harmonic distortion produced by the player.

This parameter directly characterizes the amount of distortion introduced by the device into the original sound: the lower the coefficient, the clearer the sound, the less such distortion. It is impossible to completely eliminate them, but they can be reduced to a level that is practically not perceived by a person. So, it is believed that distortions at the level of 0.5% are already invisible even to an experienced listener. At the same time, in modern audio technology, there are also much lower values \u200b\u200b- up to ten thousandths of a percent. In the case of players, such indicators play mainly an advertising role — they are a sign of a high level of the device.

Note that the coefficient of harmonic distortion is indicated mainly for Hi-Fi players (see "Type"), for which the maximum purity of sound is critical; in conventional models, it is of secondary importance.

Codecs and additional audio processing technologies supported by the Bluetooth-connected player. Initially, sound transmission via Bluetooth involves quite strong signal compression, which can greatly spoil the experience when listening to music. To eliminate this drawback, various technologies are used, in particular aptX, aptX HD, aptX Low Latency, aptX Adaptive, AAC, LDAC, LHDC. Of course, to use any of the technologies, it must be supported not only by the player, but also by the Bluetooth device with which it is used. Here are the main features of each option:

- aptX. A Bluetooth codec designed to significantly improve the quality of audio transmitted over Bluetooth. According to the creators, it allows you to achieve quality comparable to Audio CD (16-bits/44.1kHz). The benefits of aptX are most noticeable when listening to high-quality content (such as lossless formats), but even on regular MP3 it can provide a noticeable sound improvement.

- aptX HD. Development and improvement of the original aptX, allowing for sound purity comparable to Hi-Res audio (24-bits/48kHz). As in the original, the benefits of aptX HD are noticeable mainly on high-quality audio, although this codec will not be out of place for MP3.

...- aptX Low Latency. A specific version of aptX described above, designed not so much to improve sound quality, but to reduce delays in signal transmission. Such delays inevitably occur when working via Bluetooth; They are not critical for listening to music, but when watching video, there may be a noticeable desynchronization between the image and sound. The aptX LL codec eliminates this phenomenon, reducing latency to 32 ms - a difference that is imperceptible to human perception.

- aptX Adaptive. Further development of aptX; actually combines the capabilities of aptX HD and aptX Low Latency, but is not limited to this. One of the main features of this standard is the so-called adaptive bitrate: the codec automatically adjusts the actual data transfer rate based on the characteristics of the broadcast content and the congestion of the frequencies used. This, in particular, helps reduce energy consumption and increase communication reliability; and special algorithms allow you to broadcast sound quality comparable to aptX HD (24 bits/48 kHz), using much less transmitted data.

- A.A.C. A Bluetooth codec used primarily in portable Apple gadgets. In terms of capabilities, it is noticeably inferior to more advanced standards like aptX or LDAC: the sound quality when using AAC is comparable to an average MP3 file. However, for listening to the same MP3s, this is quite enough; the difference becomes noticeable only on more advanced formats.

— LDAC. Sony's proprietary Bluetooth codec. It surpasses even aptX HD in terms of bandwidth and potential sound quality, providing performance at the Hi-Res level of 24-bits/96kHz audio; There is even an opinion that this is the maximum quality that makes sense to provide for in wireless transmission - further improvement will be simply imperceptible to the human ear.

- LHDC. LHDC (Low latency High-Definition audio Codec) is a high-definition, low-latency codec developed by the Hi-Res Wireless Audio Alliance and Savitech. The codec is also known as HWA (Hi-Res Wireless Audio). When using LHDC, signal transmission is carried out with a bits rate of up to 900 kbps, a bits depth of up to 24 bits and a sampling frequency of up to 96 kHz. This ensures a stable and reliable connection with reduced latency. The codec is optimally suited for high-end wireless headphones and advanced digital audio formats.

- CUE support. The player's ability to recognize and use .cue files. Initially, such files were used as lists of tracks on an Audio CD; the sequence of tracks, their duration and name were recorded in them; Nowadays, .cue files often accompany albums and collections recorded on the principle of “all tracks in a row in one audio file.” If the player supports CUE, then you can listen to such an audio file on it as a set of separate tracks, switching between them at will - the player will take data from the .cue file about the starting point of each track and automatically skip playback. In other words, the listening format will be the same as when playing music in the “one file per track” format.

— Lossless formats. The player supports audio formats that use lossless compression. Unlike lossy compression (including MP3), with this compression the sound is not cut down, all its details are preserved as much as possible. Nowadays, there are several lossless formats, the most popular are FLAC and APE (see “Supports audio formats”); The specific set of standards with which the player is compatible should be clarified separately. However, in any case, this function will be useful to those who value the most complete and reliable sound. It is worth considering two nuances. Firstly, lossless files are quite large - one album can ta...ke up several hundred megabytes. Secondly, in order to fully appreciate such sound, you will need high-quality headphones, and ideally a Hi-Fi player (see “Type”).

— Formats without compression (uncompressed). The player supports audio formats that do not require data compression. Most of these standards are professional; they provide very high quality and reliability of sound, but they also take up a lot of space. Examples of uncompressed formats include DSD and DXD (see “Supports Audio”).

— Work in DAC mode. The ability of the player to operate in digital-to-analog converter (DAC) mode - when the device receives a digital audio signal from an external source (usually a computer USB port) and outputs analog audio. This function is found mainly in Hi-Fi models (see “Type”). It will be useful primarily when outputting sound from PCs, laptops or portable gadgets: the native sound cards in such models are often quite “weak”, and when using an external DAC you can achieve much better sound quality.

— Equalizer. This function allows you to adjust the sound volume of individual frequency bands, thus changing the overall color of the sound. Equalizers in modern players can have a different number of bands - from 2 (low and high frequencies) in the simplest models to 8 - 10 in advanced ones. In any case, such a setting can be useful both for adjusting the sound to your own preferences, and for compensating for the shortcomings of connected headphones or speakers - if they “fail” certain frequency bands. In addition, many players have a set of equalizer presets (presets), usually designed for different styles of music - “Classical”, “Rock”, “Pop”, etc.

- FM receiver. Built-in tuner for receiving radio broadcasts in the FM range. It is this range that the vast majority of modern music radio stations use, since it allows broadcasting sound in stereo format. However, some player models also support other standards - for example, AM, in which talk stations are widely represented. To listen to the radio, you usually need to connect headphones - their wire acts as an antenna.

— Recording from an FM receiver. Possibility of recording radio programs received by the player’s own tuner (see above). This function is useful if you want to “save for history” some event from the broadcast - an interesting talk show, a live performance of your favorite band in the radio station’s studio, a live call, etc.

- Dictaphone. The player can operate in voice recorder mode to record sound. Typically, the built-in microphone is used. The general functionality of such a recording is noticeably more modest than in specialized voice recorders, but for simple tasks it may well be useful.

— Built-in speaker. Its own built-in speaker allows you to listen to music without connecting headphones or speakers. In some situations - for example, when watching a movie together from the player screen - this function can be very useful. However, it is worth considering that the capabilities of the built-in speaker are usually quite modest; as a result, the volume and sound quality are low.

- Digital camera. Your own digital camera that allows you to use the player to take photos and videos. The quality of filming in most cases is not high, but there are exceptions - some player models are not inferior to middle-class smartphones in this indicator. In addition, the cameras in this case are intended not so much for highly artistic filming, but for “capturing the moment.” It is also worth noting that the location of the camera may vary. Most often it is installed on the back side, but there are also players with front cameras that allow you to take selfies and use video calling. And the most advanced players (usually models with OS, see above) may have a pair of cameras - main and front.

The player supports Bluetooth technology.

This technology is designed for direct wireless communication between different devices. There are different ways to implement it in players. The most common option is to broadcast sound to wireless headphones, acoustics or other similar equipment (aptX is highly desirable, see “Features/capabilities”). Other methods of application may also be envisaged - in particular, exchanging files with other devices and remote control (player or from the player). The specific set of additional functions should be clarified separately.

Bluetooth wireless protocols from the 4th revision and newer are relevant today:

• Bluetooth v 4.0. Revision 4.0 introduced a Bluetooth Low Energy (BLE) connection mode with low power consumption. This communication standard is intended mainly for transmitting small amounts of information - in particular, service data packets to maintain a connection. At the same time, the creators managed to combine economical energy consumption and a long communication range - it can reach 100 m, which has a positive effect on the stability of the connection.
• Bluetooth v4.1. Development and improvement of Bluetooth 4.0. In terms of players, the key innovation in this version was improved noise immunity when working near 4G (LTE) mobile communication devices (in earlier standards, Bluetooth and LTE signals could overlap, which led to failures).
• Bluetooth v4.2. Further..., after 4.1, development of the Bluetooth standard, which mainly presented a number of general improvements in the reliability and noise immunity of the connection.
• Bluetooth v5.0. Major Bluetooth update released in 2016. One of the most notable innovations was the introduction of two additional operating modes of Bluetooth LE: an increased speed mode (by reducing the range) and an extended range mode (by reducing the speed). The key benefit of these innovations is to improve the overall reliability of communications, increase their range and reduce the number of breaks.
• Bluetooth v5.1. Update to revision v 5.0, in which, in addition to general improvements in the quality and reliability of communication, it became possible to determine the direction from which the Bluetooth signal is coming. Thanks to this, the location of connected devices is determined with centimeter accuracy, which has a positive effect on the quality of the wireless connection.
• Bluetooth v5.2. The next update, after 5.1, is Bluetooth 5th generation. The main innovations in this version are a number of security improvements, additional optimization of power consumption in LE mode and a new audio signal format for synchronizing parallel playback on multiple devices.
• Bluetooth v5.3 came into use at the dawn of 2022. Among the innovations in it, they accelerated the process of negotiating a communication channel between the controller and the device, implemented the function of quickly switching between the operating state in a low duty cycle and a high-speed mode, and improved the throughput and stability of the connection by reducing susceptibility to interference. When unexpected interference occurs in Low Energy mode, the procedure for selecting a communication channel to switch from now on has been accelerated.
• Bluetooth v 5.4 was introduced at the beginning of 2023. This edition has increased the range and speed of data exchange. Also in Bluetooth v 5.4, the energy-saving BLE mode has been improved. This version of the protocol uses new security features to protect data from unauthorized access, has increased connection reliability by selecting the best channel for communication, and prevents connection losses due to interference.